Method for controlling a device for treating the human eye

ABSTRACT

The invention relates to a method for controlling a device for the treatment or refractive correction of the human eye by means of an electronic computer. The aim of the invention is to create a method for controlling a device for treating the human eye, which provides a simple overview of the influence of all of the parameters. To this end, once the operating parameters have been determined, a graphical simulation of the operating procedure is carried out in the form of a graphical visualization.

The present invention relates to a method for controlling a device forthe ablation of parts of the human eye, in particular the cornea, bymeans of laser irradiation, the control being exercised by an electronicdata-processing system which provides data to a device for treating thehuman eye by means of laser irradiation, and a device for treating thehuman eye by means of laser irradiation.

In ophthalmic surgery a series of methods are known which make possible,with or without additional invasive procedures, an abrasion of parts ofthe cornea surface to correct sight defects. In particular the PRK,LASIK and LASEK methods may be named here.

Traditionally, fine tuning of the refractive correction is carried outin the case of sphere and cylinder on the basis of subjective phoroptermeasurements, because the best possible standard correction can therebytake place in individually secured manner without taking higheraberrations into account. In the meantime, higher aberrations can besubjectively evaluated with the help of a so-called phase-platephoropter which is known for example from DE10103763, or adaptivephoropters, and used for refractive correction.

A problem when carrying out such treatment procedures is the fact thatslight changes in the treatment parameters can have a marked effect onthe success of the treatment. Reliance is usually placed here on theexperience of the doctor in attendance, the assumption being that he isaware of the significance of the effect of all the parameters.

The object of the present invention is therefore to provide a method forcontrolling a device for treating the human eye which provides a simpleoverview of the effect of all the parameters.

This problem is solved by a method according to claim 1. It is providedaccording to the invention that once the optical and geometric eye datahave been established a graphic simulation of the ablation is carriedout in the form of a graphic visualization. During the graphicvisualization, in particular the pachymetry of the cornea before andafter the treatment procedure is represented graphically. The opticaland geometric eye data are in particular thickness (pachymetry) and alsothe curvature of the cornea (topography). These data can be summarizedfor each eye in a pachymetry map and a topography map. In this way, thedoctor in attendance can graphically anticipate the result of thetreatment procedure and in particular recognize problem areas. Inaddition, problems that can be expected, such as too small a residualthickness of the cornea in part areas, can be established by thecomputer software used and displayed as a warning. In particular for thecorrection of several sight defects, an optimum parameter configurationcan be discovered with the help of the method according to theinvention, for example by varying one or more parameters. This makes itpossible to optimize the ablation for example to a minimum abrasion ofthe cornea. All the parameters can be entered or automatically recordedby means of the computer software which contains all the reciprocalrelationships and which can thus calculate a correction which takes allthe relevant factors into account. However the weighting and selectionof the parameters is not unequivocal, but determined by variouspatient-specific objectives; e.g. best sight during the day, best sightat dusk, smallest corneal abrasion or similar. The computer softwarepreferably includes an operating interface with the help of which, usingthe weighting presented previously, the doctor can swiftly arrive at anoptimum correction. A mode can also be selected which makes possible amanual adjustment of all parameters, e.g. via scroll boxes or similardisplayed on the operating interface. The effect of the parameterchanges is illustrated directly via a graphic simulation of thecorrection.

All the treatment parameters that are to be entered manually arepreferably entered by means of a central input/output device. This canbe for example a computer screen connected to a keyboard or a so-calledtouch screen.

In a development of the method according to the invention it is providedthat the establishment of the operating parameters comprises one or moreof the following process steps: establishment of topography data of theeye; establishment of refraction data of the eye; establishment ofhigher-order aberration data by wave-front measurement; establishment ofpachymetry data; establishment of the pupillometry of the eye(preferably for various lighting conditions); point-accurate overlayingof all established measurement data in a fixed coordinates system of theeye; calculation of height data of the deviations relative to areference surface; calculation of a height data difference relative tothe reference surface; calculation of an adapted height data differencerelative to the reference surface; calculation of ablation coordinatesfor the laser.

K values and/or a curvature map and/or a topography map and/or a powermap are preferably obtained from the topography data. The sphericaland/or cylindrical refraction correspondingly form part of the data forcontrolling the ablation device. The reference surface is freelyselectable as regards the topography data, preferably an ellipsoid, inthe case of the ellipsoid the reference surface of the refraction datais correspondingly a spheroid. When establishing the pupillometry, i.e.in particular the diameter of the pupil, parameters of the variouslighting conditions are preferably included, as the pupil diameterchanges depending on the lighting. The deviation of the centre of thepupil can thus shift by up to 0.5 mm under different lightingconditions. Additional parameters such as special patient wishesregarding visual acuity distribution or similar are included in theadapted height data difference. As a result of the overlaying of thesemeasurement data in a fixed coordinates system of the eye, the overallcorrection of the eye can be shown in one representation.

In a development of the method according to the invention it is providedthat in a further intermediate step, height data deviations of thecornea surface relative to a reference surface are calculated from thetopography and/or refraction data. The height data are stored as aheight data map of the deviations and can be visualized graphically.

In a development of the method according to the invention it is providedthat in a further intermediate step the tissue to be abraded from thecornea is determined from the height data of the deviations of thecornea surface.

In a preferred version the device for treating the human eye includes alaser and/or means for wave-front measurement.

The problem named at the outset is also solved by a device for treatingthe human eye by means of laser irradiation comprising an apparatus formeasuring aberrometry, an apparatus for measuring topography, anapparatus for measuring pachymetry, optionally an apparatus formeasuring pupillometry, an apparatus for point-accurate, centredoverlaying of the measurement data of all the measuring equipment of alaser unit and also an electronic data-processing apparatus which byusing a treatment model can link the measurement values and furtherpatient data to ablation values. This device preferably also includes anapparatus for measuring the pupillometry of the eye, i.e. apupillometer. The device preferably includes a measuring equipmentarrangement which allows the measurement of aberrometry, topography,pupillometry and pachymetry by means of a fixing, i.e. in apoint-accurate reference of the measurement data to a centred fixedcoordinates system of the eye. For this, the device has a combination ofthe necessary measuring instruments which make possible a measurement ofthe eye to be treated via a common eyepiece or overlay all separatemeasurement data centred vis-à-vis a location-specific coordinatessystem and display them together in their interaction. This ispreferably carried out by determining the optical axis or the visualaxis of the eye during the measurements using each individual measuringapparatus and then using these to display all the measurement datapoint-accurate, centred, overlaid. For this, the application of marks tothe eye can be envisaged, for example colour dots to which eachmeasuring apparatus or each measurement with the individual integratedmeasuring apparatus can orientate itself and refer. It is also possibleto use the texture of the iris, in particular the unchangeable areas ofthe iris, or the texture of the veins in the sclera, as fixed parametersduring the measurement. The treatment model is realized as a softwaremodule. By treatment model is meant that the software can calculate, onthe basis of the measured or manually entered parameters, the ablationfor each individual point of the cornea surface. A weighting of all themeasurement values or parameters is carried out by the software. Thesoftware thus represents a central recording and evaluation tool. Theablation for each point of the cornea surface produces an ablation map,i.e. a “chart” with which the surface can be displayed. The device ispreferably capable of displaying the ablation for each point graphicallysummarized as an ablation map.

The measuring instruments can also be arranged at least partlyseparately, their measurement results having to be imported manuallyinto the device, or connected to the device by means of a data bus suchas e.g. a serial cable so that their data can be automatically imported.

Advantageous designs of the invention are explained further in thedrawings. There is shown in:

FIG. 1 a flowchart of the method;

FIG. 1 shows a flowchart of the method according to the invention.Initially, the optical data of the eye are recorded in a first step. Forthis the topography is initially established in the form of K values, acurvature map, a topography map and a power map of the cornea. Pupildata and centring data such as the line of view (visual axis of the eye)are also included.

In a next step, objective and subjective refraction data, namely thespherical and cylindrical refraction of the patient, are established.Objective refraction data are data which are established exclusively bymeasuring with a measuring apparatus. This can be for example by meansof a refractometer or aberrometer. Subjective refraction data are datawhich are based on the feedback from the patient, who reports whether apotential correction is found to be “better” or worse. This is achievedfor example by using a phoropter which displays potential correctionscenarios on which the patient comments.

With refractive correction of the cornea based on aberrometricwave-front data it must be taken into account that an aberrometermeasurement is an objective measuring process. However, due to thephysiological process of vision, the quality of the individual sight isultimately fixed, not only by the objective optical quality of theoptical system, the eye, but additionally by the subjectively evaluatedvisual faculty.

With the device according to the invention and the method according tothe invention, it is provided to also allow, in addition to aberrometry,topography, pachymetry, pupillometry, fixing/centring, registration(this is a point-accurate allocation of the measurement data of the eyeto position the therapeutic correction, e.g. via local marks on thecornea or significant structures of the eye such as veins or irisstructures) and phoropter, a subjective evaluation of the refractionwith the help of a phase-plate or adaptive phoropter and an acuityprojector to play a part.

In a simplified method the subjective evaluation of the higher-orderaberrations can be excluded, e.g. by means of Zernike polynomials, usingthe sphere and cylinder values determined with a refractometer and/orsubjectively evaluated with a phoropter as a base data set for therefractive correction. In addition this base data set is supplemented bythe objectively measured data of higher-order Zernike polynomials whichare corrected by the spherical equivalent portions from the wave-frontdata. The higher aberration orders have a particular role in theproduction of aspherical lens profiles or correction profiles. Thesimplified method represented above can also be carried out directly onthe basis of height data instead of the wave-front/data calculationbased on Zernike polynomials. These aberrometer-aided height data arecustomary in the measurement data output of topography equipment and areobtained in aberrometers with the help of “zonal reconstruction”.Compared with data exchange on the basis of Zernike polynomials, theyguarantee a higher spatial resolution of the wave front. Uncertaintieswith regard to the correct wave-front reconstruction in polynomialdescription can be largely avoided depending on the resolution of thezonal reconstruction. So-called “repair cases” can thus be realizedbased on a complete data set of the overall optical system. Also on thebasis of these wave-front height data, it must be taken into accountwithin the framework of the described simplified method that in additionto the base data set the wave-front data can also be supplemented asequivalent portions without the spherical and cylindrical base portions.

In individually optimized treatment based on the method according to theinvention, a higher quality of the refractive correction of the corneais achieved in particular by combining the produced measurement data ofthe whole wave front and the topography of the cornea based on apolynomial breakdown, e.g. according to Zernike or Taylor and/or theheight data. In this way, the refractive correction can be designed inconsideration of the special characteristics of the different opticalpart-systems of the eye. Particular consideration is given to the corneawhich delivers the main refracting power of the eye at approx. 80% andsimultaneously forms the ablation target for refractive laser surgery.Thus in a simplified model the projection effects of the ablative laserspot on the spherical surface of the cornea can be taken into accountfor a radius of approx. 7.8 mm over a keratometric radius measurement ofthe cornea. A still more precise control of the ablation inconsideration of the projective fluence variations of the laser spot onthe cornea is obtained when the topography is taken into account. Thusnot only can the ablation be controlled by the method according to theinvention, in consideration of a keratometrically established radius ofthe cornea in order to balance out the projective fluence variations ofthe laser spot in particular at the margins of the ablation, but thetopography data which describe the surface more accurately can also beused for this.

The higher-order aberrations are objectively established by means of awave-front measurement. Known devices and methods for wave-frontmeasurement can be used for this.

In a further step, height data of the deviations of the cornea surfacerelative to a reference surface are calculated from the thus-establishedrefraction or topography data. They are established from refractiondata, applying the standard algorithms, for example the Munnerlynformulae. A sphere is used as assumed reference surface.

In a further step the height data are derived from the topography data.The curvature of the reference surface is established using therefraction data. Here too the data are calculated using standardalgorithms such as Munnerlyn formulae. The K values are also taken intoaccount here. An ellipsoid is used as assumed reference surface.

In a further step, the refraction data are linked to the data of thewave-front measurement. The curvature of the reference surfaces isestablished using the refractive data. The subjective refractions arecalculated applying standard algorithms such as the Munnerlyn formulaeand overlaying the thus-established data with high-order (HO) data. Asphere is used as assumed reference surface.

In a third step the refraction data are linked to the topography dataand the data of the wave-front measurement. Here too these values areoverlaid with high order data in consideration of the K values applyingstandard algorithms such as the Munnerlyn formulae. An ellipsoid is usedhere as assumed reference surface. The difference in the topography datavis-à-vis the data established with the wave front measurement isproblematic.

In a further step the height data difference relative to the referencesurface is now calculated. A chart (data map) is calculated with heightdata relative to the deviations to the reference surface. The heightdifference relative to the reference surface, and thus the tissue to beabraded is given for each point of the cornea surface.

When applying the LASIK procedure, the flap thickness, the flap diameterand the direction of the fold (hinge side) of the flap are determined.Furthermore, data relating to pachymetry, the thickness of the cornea,are included in the form of a pachymetry map. The effects of pachymetryon the ablation depth are determined. In addition, further patient datasuch as the age and the cylinder data of the patient are included.Effects on the correction of the refraction and correction of thecylinder axis are also calculated from these.

Depending on the method to be carried out, for example PRK or LASIK,process-typical effects on the nomograms and the refraction areestablished.

In addition certain optimizations are taken into account, e.g. TSA,Night Vision, ASAP grade. A reference surfaces fit is brought about ineach zone with a Z shifting.

With the parameters shown above, patient-adapted (customized) heightdata differences relative to the reference surface are established fromthe height data difference relative to the reference surface. Thisresults in an adapted data map with height data of the deviationrelative to the reference surface. The ablation algorithms are realizedwith these data. This produces as a result the output of the residualthickness, the ablation volume and the residual defect.

In addition to the previously established data the influences of thelaser parameters, in particular the energy density distribution, thefiring frequency, the spot geometry and also the resolution accuracy ofthe scanner are taken into account. In addition the data with regard tosmoke and thermal problems are incorporated.

In addition, reflection and projection data are established, inparticular the change in energy density distribution and reflectionlosses. This yields correction data for the ablation target data.

Finally, ablation coordinates for the laser are issued, in this casecoordination data for specific lasers (for example MEL 70).

The established and calculated data can be issued on a computer screenin the form of a graphic simulation. The simulation displays the corneato be treated for example in different colours or similar in top view orin section so that the doctor in attendance can assess the wholeprocedure in advance.

Thus it is possible with this device or the electronic data-processingsystem which consists either of a networked or compact integratedmeasuring equipment system to record all the objective and subjectivedata of the optical refraction and geometry of the eye is such a waythat they are stored or displayed overlaid centred and point-accurate ina fixed coordinates system of the eye.

1-13. (canceled)
 14. A method for controlling a device for an ablationof a part of a human eye using laser irradiation, the control beingexercised using an electronic data processing system, the methodcomprising: determining optic and geometrical data of the eye; andperforming a graphic simulation of the ablation in the form of a graphicvisualization.
 15. The method as recited in claim 14, further comprisinginputting a plurality of treatment parameters manually using a centralinput/output device.
 16. The method as recited in claim 15, furthercomprising determining a plurality of operating parameters, wherein thedetermining includes at least one of: a) establishing a topography dataof the eye; b) establishing a refraction data of the eye; c)establishing a higher-order aberration data of the eye using wave-frontmeasurement; d) establishing a pachymetry data of the eye; e)establishing a pupillometry data; f) point-accurate overlaying of allthe measurement data from a) through e) in a fixed coordinates system ofthe eye; g) calculating a height data of deviations relative to areference surface; h) calculating a height data difference relative tothe reference surface; g) calculatiing an adapted height data differencerelative to the reference surface; h) calculating ablation coordinatesfor the device, wherein the device includes a laser.
 17. The method asrecited in claim 16, wherein the establishing of the refraction dataincludes establishing at least one of a subjective and an objectiverefraction data.
 18. The method as recited in claim 16, furthercomprising calculating a height data of deviations of a cornea surfaceof the eye relative to a reference surface using at least one of thetopography data and the refraction data.
 19. The method as recited inclaim 18, further comprising determining a tissue to be abraded from thecornea of the eye using the height data of the deviations of the corneasurface.
 20. The method as recited in claim 16, further comprisingdetermining a result using the topography data, the result including atleast one of a K value, a curvature map, a topography map, and a powermap, and wherein the controlling the device for the ablation isperformed using the result.
 21. The method as recited in claim 16,wherein the establishing of the refraction data of the eye includesestablishing at least one of spherical refraction data and cylindricalrefraction data.
 22. The method as recited in claim 16, wherein thereference surface is an ellipsoid.
 23. The method as recited in claim16, wherein a refraction reference surface of the refraction data is aspheroid.
 24. The method as recited in claim 14, wherein the device forablation includes at least one of a laser and a wave-front measurementdevice.
 25. A device for treating a human eye using laser irradiation,the device comprising: a aberrometry apparatus configured to measure anaberrometry of the eye; a topography apparatus configured to measure atopography of the eye; a pachymetry apparatus configured to measure apachymetry of the eye; an overlaying apparatus configured to provide apoint-accurate, centred overlaying of the aberrometry, topography, andpachymetry; a laser unit; and an electronic data-processing apparatusconfigured to link the aberrometry, topography, pachymetry and furtherpatient data to ablation values using a processing model.
 26. The deviceas recited in claim 24, further comprising a pupillometry apparatus formeasuring a pupillometry of the eye.
 27. The device as recited in claim25, wherein the aberrometry apparatus, the topography apparatus, thepachymetry apparatus, and the pupillometry apparatus are disposed in ameasuring equipment arrangement configured to allow measurement ofaberrometry, topography, pupillometry and pachymetry using a fixing. 28.The device as recited in claim 24, wherein the device is configured todisplay an ablation of the eye graphically as an ablation map.